1,652 research outputs found
Searching for the expelled hydrogen envelope in Type I supernovae via late-time H-alpha emission
We report the first results from our long-term observational survey aimed at
discovering late-time interaction between the ejecta of hydrogen-poor Type I
supernovae and the hydrogen-rich envelope expelled from the progenitor star
several decades/centuries before explosion. The expelled envelope, moving with
a velocity of ~10 -- 100 km s, is expected to be caught up by the
fast-moving SN ejecta several years/decades after explosion depending on the
history of the mass-loss process acting in the progenitor star prior to
explosion. The collision between the SN ejecta and the circumstellar envelope
results in net emission in the Balmer-lines, especially in H-alpha. We look for
signs of late-time H-alpha emission in older Type Ia/Ibc/IIb SNe having
hydrogen-poor ejecta, via narrow-band imaging. Continuum-subtracted H-alpha
emission has been detected for 13 point sources: 9 SN Ibc, 1 SN IIb and 3 SN Ia
events. Thirty-eight SN sites were observed on at least two epochs, from which
three objects (SN 1985F, SN 2005kl, SN 2012fh) showed significant temporal
variation in the strength of their H-alpha emission in our DIAFI data. This
suggests that the variable emission is probably not due to nearby H II regions
unassociated with the SN, and hence is an important additional hint that
ejecta-CSM interaction may take place in these systems. Moreover, we
successfully detected the late-time H-alpha emission from the Type Ib SN 2014C,
which was recently discovered as a strongly interacting SN in various (radio,
infrared, optical and X-ray) bands.Comment: 8 pages, 7 figures, accepted in Ap
Long-lived, long-period radial velocity variations in Aldebaran: A planetary companion and stellar activity
We investigate the nature of the long-period radial velocity variations in
Alpha Tau first reported over 20 years ago. We analyzed precise stellar radial
velocity measurements for Alpha Tau spanning over 30 years. An examination of
the Halpha and Ca II 8662 spectral lines, and Hipparcos photometry was also
done to help discern the nature of the long-period radial velocity variations.
Our radial velocity data show that the long-period, low amplitude radial
velocity variations are long-lived and coherent. Furthermore, Halpha equivalent
width measurements and Hipparcos photometry show no significant variations with
this period. Another investigation of this star established that there was no
variability in the spectral line shapes with the radial velocity period. An
orbital solution results in a period of P = 628.96 +/- 0.90 d, eccentricity, e
= 0.10 +/- 0.05, and a radial velocity amplitude, K = 142.1 +/- 7.2 m/s.
Evolutionary tracks yield a stellar mass of 1.13 +/- 0.11 M_sun, which
corresponds to a minimum companion mass of 6.47 +/- 0.53 M_Jup with an orbital
semi-major axis of a = 1.46 +/- 0.27 AU. After removing the orbital motion of
the companion, an additional period of ~ 520 d is found in the radial velocity
data, but only in some time spans. A similar period is found in the variations
in the equivalent width of Halpha and Ca II. Variations at one-third of this
period are also found in the spectral line bisector measurements. The 520 d
period is interpreted as the rotation modulation by stellar surface structure.
Its presence, however, may not be long-lived, and it only appears in epochs of
the radial velocity data separated by 10 years. This might be due to an
activity cycle. The data presented here provide further evidence of a planetary
companion to Alpha Tau, as well as activity-related radial velocity variations.Comment: 18 pages, 14 figures. Accepted for publication in Astronomy and
Astrophysic
Exploring The Frequency Of Close-In Jovian Planets Around M Dwarfs
We discuss our high precision radial velocity results of a sample of 90 M dwarfs observed with the Hobby-Eberly Telescope and the Harlan J. Smith 2.7 m Telescope at McDonald Observatory, as well as the ESO VLT and the Keck I telescopes, within the context of the overall frequency of Jupiter-mass planetary companions to main sequence stars. None of the stars in our sample show variability indicative of a giant planet in a short period orbit, with a 3.8 M_Jup and a 3.5 M_Jup and a < 0.7 AU. Our results point toward a generally lower frequency of close-in Jovian planets for M dwarfs as compared to FGK-type stars. This is an important piece of information for our understanding of the process of planet formation as a function of stellar mass
A Novel Clustering Algorithm Based on Quantum Games
Enormous successes have been made by quantum algorithms during the last
decade. In this paper, we combine the quantum game with the problem of data
clustering, and then develop a quantum-game-based clustering algorithm, in
which data points in a dataset are considered as players who can make decisions
and implement quantum strategies in quantum games. After each round of a
quantum game, each player's expected payoff is calculated. Later, he uses a
link-removing-and-rewiring (LRR) function to change his neighbors and adjust
the strength of links connecting to them in order to maximize his payoff.
Further, algorithms are discussed and analyzed in two cases of strategies, two
payoff matrixes and two LRR functions. Consequently, the simulation results
have demonstrated that data points in datasets are clustered reasonably and
efficiently, and the clustering algorithms have fast rates of convergence.
Moreover, the comparison with other algorithms also provides an indication of
the effectiveness of the proposed approach.Comment: 19 pages, 5 figures, 5 table
CoRoT-22 b: a validated 4.9 RE exoplanet in 10-day orbit
The CoRoT satellite has provided high-precision photometric light curves for
more than 163,000 stars and found several hundreds of transiting systems
compatible with a planetary scenario. If ground-based velocimetric observations
are the best way to identify the actual planets among many possible
configurations of eclipsing binary systems, recent transit surveys have shown
that it is not always within reach of the radial-velocity detection limits. In
this paper, we present a transiting exoplanet candidate discovered by CoRoT
whose nature cannot be established from ground-based observations, and where
extensive analyses are used to validate the planet scenario. They are based on
observing constraints from radial-velocity spectroscopy, adaptive optics
imaging and the CoRoT transit shape, as well as from priors on stellar
populations, planet and multiple stellar systems frequency. We use the fully
Bayesian approach developed in the PASTIS analysis software, and conclude that
the planet scenario is at least 1400 times more probable than any other false
positive scenario. The primary star is a metallic solar-like dwarf, with Ms =
1.099+-0.049 Msun and Rs = 1.136 (+0.038,-0.090) Rsun . The validated planet
has a radius of Rp = 4.88 (+0.17,-0.39) RE and mass less than 49 ME. Its mean
density is smaller than 2.56 g/cm^3 and orbital period is 9.7566+-0.0012 days.
This object, called CoRoT-22 b, adds to a large number of validated Kepler
planets. These planets do not have a proper measurement of the mass but allow
statistical characterization of the exoplanet population
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX): Description and Early Pilot Survey Results
The Hobby-Eberly Telescope Dark Energy Experiment (HETDEX) will outfit the 10
m HET with a new wide field and an array of 150 integral-field spectrographs to
survey a 420 sq. deg. area in the north Galactic cap. Each fiber-coupled unit
spectrograph will cover 350-550 nm, simultaneously. This instrument, called
VIRUS, will produce ~34,000 spectra per exposure, and will open up the
emission-line universe to large surveys for the first time. The survey will
detect 0.8 million Lyman-alpha emitting (LAE) galaxies with 1.9<z<3.5 and more
than a million [OII] emitting galaxies with z<0.5.
The 3-D map of LAE galaxies in 9 cubic Gpc volume will be used to measure the
expansion history at this early epoch using baryonic acoustic oscillations and
the shape of the power spectrum. The aim of HETDEX is to provide a direct
detection of dark energy at z~3. The measurement will constrain the evolution
of dark energy and will also provide 0.1%-level accuracy on the curvature of
the Universe, ten times better than current.
The prototype of the VIRUS unit spectrograph (VIRUS-P) is a powerful
instrument in its own right. Used on the McDonald 2.7 m, it covers the largest
area of any integral field spectrograph, and reaches wavelengths down to 340
nm. VIRUS-P is being used for a pilot survey to better measure the properties
of LAE galaxies in support of HETDEX. We report initial results from this
survey.Comment: 4 pages, 1 Postscript figure. Paper presented at conference
"Panoramic Views of the Universe", Hayama, Japan, December 2007 (ASP
Conference Series, in press
Maintenance treatment of adolescent bipolar disorder: open study of the effectiveness and tolerability of quetiapine
<p>Abstract</p> <p>Background</p> <p>The purpose of the study was to determine the effectiveness and tolerability of quetiapine as a maintenance treatment preventing against relapse or recurrence of acute mood episodes in adolescent patients diagnosed with bipolar disorder.</p> <p>Methods</p> <p>Consenting patients meeting DSM-IV lifetime criteria for a bipolar disorder and clinically appropriate for maintenance treatment were enrolled in a 48-week open prospective study. After being acutely stabilized (CGI-S ≤ 3 for 4 consecutive weeks), patients were started or continued on quetiapine and other medications were weaned off over an 8-week period. Quetiapine monotherapy was continued for 40-weeks and other mood stabilizers or antidepressants were added if clinically indicated. A neurocognitive test battery assessing the most reliable findings in adult patients was administered at fixed time points throughout the study to patients and matched controls.</p> <p>Results</p> <p>Of the 21 enrolled patients, 18 completed the 48-week study. Thirteen patients were able to be maintained without relapse or recurrence in good quality remission on quetiapine monotherapy, while 5 patients required additional medication to treat impairing residual depressive and/or anxiety symptoms. According to symptom ratings and global functioning scores, the quality of remission for all patients was very good.</p> <p>Neurocognitive test performance over treatment was equivalent to that of a matched control group of never ill adolescents. Quetiapine was generally well tolerated with no serious adverse effects.</p> <p>Conclusion</p> <p>This study suggests that a proportion of adolescent patients diagnosed with bipolar disorder can be successfully maintained on quetiapine monotherapy. The good quality of clinical remission and preserved neurocognitive functioning underscores the importance of early diagnosis and effective stabilization.</p> <p>Clinical Trials Registry</p> <p>D1441L00024</p
The spin-orbit angle of the transiting hot jupiter CoRoT-1b
We measure the angle between the planetary orbit and the stellar rotation
axis in the transiting planetary system CoRoT-1, with new HIRES/Keck and
FORS/VLT high-accuracy photometry. The data indicate a highly tilted system,
with a projected spin-orbit angle lambda = 77 +- 11 degrees. Systematic
uncertainties in the radial velocity data could cause the actual errors to be
larger by an unknown amount, and this result needs to be confirmed with further
high-accuracy spectroscopic transit measurements.
Spin-orbit alignment has now been measured in a dozen extra-solar planetary
systems, and several show strong misalignment. The first three misaligned
planets were all much more massive than Jupiter and followed eccentric orbits.
CoRoT-1, however, is a jovian-mass close-in planet on a circular orbit. If its
strong misalignment is confirmed, it would break this pattern. The high
occurence of misaligned systems for several types of planets and orbits favours
planet-planet scattering as a mechanism to bring gas giants on very close
orbits.Comment: to appear in in MNRAS letters [5 pages
Reconstructing the eclectic psychiatry of Thomas Ferguson Rodger
This article provides an introduction to the approach of the Scottish psychiatrist Thomas Ferguson Rodger (1907–78), as reconstructed from his archive. Rodger’s contribution has been largely neglected within the history of Scottish psychiatry. This paper amends this neglect through situating Rodger’s eclecticism in relation to both the biopsychosocial approach of his mentors, Adolf Meyer and David Henderson, and psychiatry’s de-institutionalization in the 1950s and 1960s. It is posited that Rodger’s eclecticism was a considered response to the pressures of this transitional phase to balance physical, psychological and social approaches, and a critical acknowledgement of the instability of contemporary psychiatric therapeutics. More psychodynamic than his predecessors, the importance of social relations for Rodger led him to acknowledge psychiatry’s limitations
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